1. Field of the Invention
This invention relates to a method and a system for shift control in an automatic transmission for a vehicle, and more particularly to improvements in a method and a system for shift control in an automatic transmission for a vehicle, wherein, during shifting, engine torque is changed by a predetermined value to thereby maintain the shift characteristics satisfactorily.
2. Description of the Prior Art
There has been widely known an automatic transmission for a vehicle constructed such that a gear shift mechanism and a plurality of frictionally engaging devices are provided, and a hydraulic control device is operated to selectively switch the engagement of the plurality of frictionally engaging devices, so that any one of a plurality of gear stages can be achieved.
In general, the automatic transmission for a vehicle of the type described is provided with a shift lever operated by a driver. In addition, in accordance with the range of the shift lever, the engagement of the frictionally engaging devices can be automatically switched in association with vehicle speed, throttle opening and the like.
Applicant has proposed various methods of controlling an engine integrally with an automatic transmission of the type described, wherein, during shifting, engine torque is changed to obtain satisfactory shift characteristics and to secure and improve the durability of the frictionally engaging devices (for example, Japanese Patent Laid-open application Ser. No. 129,341 laid open on June 17, 1986). More specifically, this integral control contemplates that, during shifting, a transmitted torque value from the engine is changed, whereby the energy absorption levels in various members in the automatic transmission or the frictionally engaging devices for braking these members are controlled to achieve a shift with a low shift shock for a short period of time, so that a satisfactory shift feeling can be provided to the driver and the frictionally engaging devices can be improved in terms of durability.
In the above-noted art, the engine torque control has been controlled in response to each shifting signal. However, in this case, for example, when quick shifting is instructed in the order of 1st gear--2nd gear--1st gear, 2nd gear--1st gear--2nd gear or the like, if the shifting is instructed before 1st shifting is substantially initiated, then engine torque control need not be performed and rather should not be performed from the viewpoint of the shift shock.